Not often, and they're only AA's, but I still got a 3rd party battery pack for my wavebird. Now, every so often, I just plug the AC adapter chord into the back of my wavebird and let it charge over night. The box it came with claims 12 continuous hours of use from it, and while I haven't played that long at one time, I'd say it more than matches that figure on non-consecutive plays.

The Wavebird is the best thing to happen to video games in a long time.